1. Field of the Invention
This invention relates to a display and a display control method and in particular to a dimmer control technique wherein outside light is converted into a voltage by a photosensor and an intensity indication voltage is read by a microcomputer for controlling the intensity of an in-car image display.
2. Description of the Related Arts
Since the brightness in an automobile changes largely depending on the environment outside the automobile, the intensity needs to be finely changed in an in-car display such as a display of a car navigation system.
In some countries, this kind of dimmer control is made compulsory.
A dimmer control technique in a related art will be discussed.
The dimmer control in the related art is adapted to change intensity L stepwise with respect to input voltage V, as shown in FIG. 7 (schematic representation of the principle of the dimmer control). In FIG. 7, the horizontal axis is the input voltage V and the vertical axis is the intensity L. However, hysteresis is provided in accordance with the solid line characteristic when the voltage rises, and is provided so as to provide the dashed line characteristic when the voltage falls. For example, if the voltage V exceeds V2, the intensity L is raised by one step from L1 to L2, but if the voltage V falls below V2, L2 is maintained on the characteristic curve indicated by the dashed line until the voltage V becomes V1 or less. If the voltage V exceeds V2, the intensity L remains to be L2 until the voltage V exceeds V3. Thus, after all, a hysteresis width is formed one step at a time above and below with V2 as the center and processing is performed so as not to cause intensity variation to occur for ripples in the range.
By the way, the accuracy required for intensity adjustment when the vehicle is driven on a flat highway, etc., where the surrounding environment less changes largely differs that when the vehicle is driven on an uneven mountain path, etc., where the surrounding environment largely changes. That is, to drive the vehicle on the highway, the light amount detection period is taken large, such as 30 minutes or one hour, and the intensity adjustment frequency may be small; to drive the vehicle on the mountain path, the light amount detection period needs to be made small for executing intensity adjustment frequently.
Rapid change in the light quantity may be received in some cases, such as reception of intermittently irregularly reflected light in the presence of a handrail, etc., rapid change when the vehicle enters a tunnel, or instantaneous light from an oncoming vehicle at the night driving time. In such cases, if the intensity of the display is adjusted in response to the instantaneous light amount, in fact the intensity adjustment speed of the dimmer does not follow and the display may enter a state hard to see.
There is a tendency to grow the display function of a display of a portable telephone with the increasing range of uses for mail, etc. Such a portable telephone may be used in various external environments. Change in outside light to use the portable telephone outside differs largely from that to use the portable telephone indoors. For example, to use the portable telephone indoors, outside light change does not occur for hours if the portable telephone is used at the same place under night illumination. In contrast, to use the portable telephone outside and moreover in a moving train, bus, etc., outside light change is extremely large.
However, in the method in the related art, the outside light detection period is constant; adjustments are made in the same period regardless of the use place of the portable telephone, namely, in the room where adjustment is not required for hours or in a moving car where the external environment changes frequently. If the period is made too small, the adjustment variable value is constant and variations in intensity adjustment speeds from one product to another cannot be absorbed and in contrast, if the detection period is taken large, sufficient adjustment cannot be made; this is a problem.
To use the portable telephone indoors, even the adjustment frequency in hour units of detection period is sufficient because outside light change is extremely small.
It is therefore a first object of the invention to provide a display control method capable of changing the adjustment frequency in response to the use environment.
It is a second object of the invention to absorb variations from one product to another and intermittent change in outside light and provide good intensity adjustments. To the ends, in the dimmer control technique of the invention, the outside light detection period is made variable and the intensity adjustment speed is changed and is made variable so as to deal with outside light change in largely different use environments, such as the inside of a room and the inside of a moving car.
When light amount change of outside light is not held a constant value or more for a constant time, even if the outside light changes, the preceding value of intensity is maintained, thereby absorbing intermittent change in the outside light caused by a handrail, etc.
According to a first aspect of the invention, there is provided a display control method for adjusting intensity of an image display in accordance with time change of outside light, the display control method comprising the steps of detecting the light amount of the outside light and adjusting the intensity in response to the detected light amount, characterized in that the detecting step comprises the variable period setting step of setting a read period and the detecting step of detecting the light amount every period set at the setting step.
According to the Configuration, appropriate intensity adjustment can be made in response to the use environment and an easy-to-see display image can be provided. For example, with a portable telephone, change in outside light to use the portable telephone outside differs largely from that to use the portable telephone indoors. In such a case, for example, to use the portable telephone indoors, the read period is set large, such as one hour or two hours; to use the portable telephone outside and moreover in a moving train, bus, etc., the period is lessened, so that it is made possible to control in response to the use environment.
According to a second aspect of the invention, there is provided a display control method for adjusting intensity of an image display in accordance with time change of outside light, the display control method comprising the steps of detecting the light amount of the outside light and adjusting the intensity in response to the detected light amount, characterized in that the detecting step comprises the processing step of changing the intensity only if light amount change of the outside light is held a constant value or more for a constant time, thereby absorbing intermittent change in the outside light.
According to the method, if abrupt change of intermittent irregular reflection caused by a handrail, etc., noise, or the like is detected, no intensity adjustment is made and only when the light amount change of the outside light holds the difference of a constant value or more for a constant time, the intensity is changed, so that it is made possible to make stable intensity adjustments. If the follow speed of a speed adjustment actuator is small because of the machine system difference of the used apparatus, the constant time can also be prolonged and resistance to adjustment is also enabled.
In a third aspect of the invention, in the display control method as claimed in claim 2, the detecting step comprises the additional steps of the variable period setting step of further setting a read period.
In a fourth aspect of the invention, in the display control method as claimed in claim 1, further comprising the processing step of changing the intensity only if light amount change of the outside light is held a constant value or more for a constant time, thereby absorbing intermittent change in the outside light.
According to the method, in addition to the advantage provided according to the first aspect of the invention, if abrupt change of intermittent irregular reflection caused by a handrail, etc., noise, or the like is detected, no intensity adjustment is made and only when the light amount change of the outside light is held a constant value or more for a constant time, the intensity is changed, so that it is made possible to make stable intensity adjustments.
In a fifth aspect of the invention, in the display control method as claimed in claim 1, the detecting step comprises the additional step of executing photoelectric conversion of the light amount of the outside light to a voltage value and outputting the light amount as the voltage value.
In a sixth aspect of the invention, in the display control method as claimed in claim 1, the variable period setting step is to read data from among data stored in a storage unit and set the read data as the read period.
According to the configuration, appropriate periods are preset in response to several situation settings and an appropriate adjustment mode can be easily set simply by selecting a situation. For example, cases are preset, outside light is converted into a voltage for each representative environment condition, the provided voltage is read by a microcomputer as input voltage, intensity control is performed, the relationship between the read period data and the reference voltage to be compared therewith is stored in a storage unit such as non-volatile memory, and data is fetched from the storage unit for performing control. In doing so, control is facilitated. Using flash memory, data can be fetched and used instantaneously and it is made possible to perform intensity control with higher accuracy.
In a seventh aspect of the invention, in the display control method as claimed in claim 2, the detecting step comprises the additional step of executing photoelectric conversion of the light amount of the outside light to a voltage value and outputting the light amount as the voltage value.
In an eighth aspect of the invention, in the display control method as claimed in claim 2, the variable period setting step is to read data from among data stored in a storage unit and set the read data as the read period.
In a ninth aspect of the invention, in the display control method as claimed in claim 2, the display is an in-car display.
According to a tenth aspect of the invention, there is provided a display controller comprising variable period setting means for setting a read period, detection means for detecting the light amount of outside light every setup read period, and intensity adjustment means for adjusting intensity of a display in response to the detected light amount of outside light.
According to an eleventh aspect of the invention, there is provided a display controller comprising detection means for detecting the light amount of outside light and intensity adjustment means for adjusting intensity of a display in response to the detected light amount of outside light, characterized in that the intensity adjustment means adjusts the intensity only if light amount change of the outside light is held a constant value or more for a constant time, thereby absorbing intermittent change in the outside light.
In a twelfth aspect of the invention, in the display controller as claimed in claim 10, characterized in that the intensity adjustment means adjusts the intensity only if light amount change of the outside light is held a constant value or more for a constant time, thereby absorbing intermittent change in the outside light.
In a thirteenth aspect of the invention, in the display controller as claimed in claim 10, characterized in that the detecting means comprises the additional means of executing photoelectric conversion of the light amount of the outside light to a voltage value and outputting the light amount as the voltage value.
In a fourteenth aspect of the invention, in the display controller as claimed in claim 10, the variable period setting means is to read data from among data stored in a storage unit and set the read data as the read period.
In a fifteenth aspect of the invention, in the display controller as claimed in claim 10, the display is an in-car display.